A fluid contact reaction device capable of continuous heat exchange and a lithium iron phosphate preparation method

Abstract

The application discloses a fluid contact reaction equipment capable of continuous heat exchange, comprising a rotary distribution valve and a plurality of reaction units; the rotary distribution valve is provided with M regions, M is greater than or equal to 2, and at least includes a temperature rising region and a temperature falling region; the temperature rising region and the temperature falling region are both provided with a heat exchange medium inlet and a heat exchange medium outlet; the reaction unit is provided with a heat exchange structure, a heat exchange inlet and a heat exchange outlet; with the rotation of the rotary distribution valve, each reaction unit can be respectively connected to the temperature rising region and the temperature falling region; when connected, the heat exchange medium inlet is connected to the heat exchange inlet, and the heat exchange medium outlet is connected to the heat exchange outlet; the temperature rising region heat exchange medium inlet and the temperature falling region heat exchange medium outlet are connected by a first heat exchange circulation pipe, and the temperature rising region heat exchange medium outlet and the temperature falling region heat exchange medium inlet are connected by a second heat exchange circulation pipe. In addition, a lithium iron phosphate preparation method is also disclosed. The application can continuously heat exchange the material liquid, accelerate the temperature rising and falling speed of the material liquid, and has high heat energy utilization rate.

Description

Technical Field

[0001] This invention relates to the field of fluid processing technology, and in particular to a fluid contact reaction device with continuous heat exchange and a method for preparing lithium iron phosphate. Background Technology

[0002] Various rotary distribution valves exist, with basic structures as shown in CN109780269A, CN108953674A, and CN109764155A, etc. They possess the function of continuously processing fluids and are primarily used in continuous ion exchange and continuous chromatographic separation. When applied in continuous ion exchange and continuous chromatographic separation, as illustrated in patents such as CN112062796A (a method for continuous desalting and neutralizing acarbose based on a continuous ion exchange device), CN114369043A (a process for preparing taurine using continuous ion exchange), and CN101643487A (a method for separating and purifying amikacin), multiple zones such as backwash water and acid regeneration zones can be correspondingly set on the rotary distribution valve according to the preparation process to handle the fluids. However, such rotary distribution valves are rarely used in other fields.

[0003] In addition, lithium iron phosphate, an existing lithium-ion battery electrode material, is inexpensive, pollution-free, and has good thermal stability, making it one of the most promising cathode materials currently available. Depending on the raw materials and preparation processes, the industrial-scale preparation of lithium iron phosphate mainly includes the following four processes:

[0004] 1. Ferrous oxalate process: Ferrous oxalate (FeC2O4·2H2O) is used as the iron source, mixed with ammonium dihydrogen phosphate or diammonium hydrogen phosphate, lithium salt, and carbon source, and then pre-decomposed and calcined at high temperature under reducing or inert atmosphere protection to produce lithium iron phosphate. The preparation process generates a large amount of ammonia gas, polluting the environment and corroding equipment. Furthermore, ferrous oxalate is a relatively expensive raw material.

[0005] 2. Iron oxide red process: Iron oxide red (Fe2O3) is used as the iron source, and mixed with lithium dihydrogen phosphate (LiH2PO4) and carbon source by wet grinding, spray drying, and high-temperature carbothermic reduction reaction under reducing or inert atmosphere protection to produce lithium iron phosphate. This process is relatively environmentally friendly, but the raw material lithium dihydrogen phosphate is expensive, and the particle size control of iron oxide red is unstable, resulting in poor batch stability of products.

[0006] 3. Iron phosphate process: Lithium iron phosphate is produced by uniformly mixing iron phosphate (FePO4) with lithium carbonate (Li2CO3) and a carbon source, and then undergoing a high-temperature carbothermic reduction reaction under reducing or inert atmosphere protection. Since LiFePO4 materials exhibit a final two-phase structure of LiFePO4 and FePO4 during charge and discharge (their crystal structures are essentially identical, with minimal changes in unit cell parameters), lithium iron phosphate materials made from iron phosphate typically have better performance.

[0007] 4. Wet Process: Lithium, iron, and phosphorus sources are dispersed in water or other solvents and reacted in a single step at relatively low temperatures and high pressures via hydrothermal or solvothermal processes to synthesize lithium iron phosphate, followed by further processing. This method is simple and generally uses a single reactor for preparation, producing nano-sized lithium iron phosphate. However, when using a single reactor to process the feed solution, the heating and cooling rates are slow, and the thermal energy utilization rate is low. Summary of the Invention

[0008] The purpose of this invention is to provide a fluid contact reaction device with continuous heat exchange capability for contact reaction of the feed liquid, and to continuously exchange heat with the feed liquid to accelerate the heating and cooling rate of the feed liquid and improve the thermal energy utilization rate. Based on this, a method for preparing lithium iron phosphate is also disclosed, in which the feed liquid heats and cools down rapidly during preparation, resulting in a high thermal energy utilization rate.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A fluid contact reaction device with continuous heat exchange includes a rotary distribution valve and multiple reaction units. The rotary distribution valve is provided with M zones, where M≥2, and each zone includes at least a heating zone and a cooling zone. Each heating zone and cooling zone is provided with a heat exchange medium inlet and a heat exchange medium outlet. Each reaction unit is provided with a heat exchange structure, and the heat exchange structure is provided with a heat exchange inlet and a heat exchange outlet for the heat exchange medium to enter and exit. As the rotary distribution valve rotates, each reaction unit can be connected to the heating zone and the cooling zone respectively. When connected, the heat exchange medium inlet connects to the heat exchange inlet of the corresponding reaction unit, and the heat exchange medium outlet connects to the heat exchange outlet of the corresponding reaction unit.

[0011] A first heat exchange circulation pipe is connected between the heat exchange medium inlet of the heating zone and the heat exchange medium outlet of the cooling zone, and a second heat exchange circulation pipe is connected between the heat exchange medium outlet of the heating zone and the heat exchange medium inlet of the cooling zone.

[0012] Furthermore, the region also includes a temperature-regulating zone and a constant-temperature zone, each of which is provided with a heat exchange medium inlet and a heat exchange medium outlet; as the rotary distribution valve rotates and switches, each reaction unit can sequentially connect to the heating zone, temperature-regulating zone, constant-temperature zone, and cooling zone.

[0013] Furthermore, the first heat exchange circulation pipe is connected to several inlet branch pipes and outlet branch pipes. The first heat exchange circulation pipe is connected to the heat exchange medium inlet in the heating zone, temperature adjustment zone and constant temperature zone through the inlet branch pipes, and is connected to the heat exchange medium outlet in the temperature adjustment zone, constant temperature zone and cooling zone through the outlet branch pipes.

[0014] Furthermore, each of the liquid inlet branch pipes corresponds to one of the heating zone, temperature adjustment zone, and constant temperature zone, and each liquid inlet branch pipe is equipped with a liquid inlet pump.

[0015] Furthermore, it also includes an expansion tank, an oil replenishment pipe, and an exhaust pipe; the expansion tank is provided with an oil filling port and an exhaust port at the top, and an oil replenishment port at the bottom; one end of the oil replenishment pipe is connected to the oil replenishment port, and the other end is connected to the first heat exchange circulation pipe, and an oil replenishment valve is provided on the oil replenishment pipe; one end of the exhaust pipe is connected to the exhaust port, and the other end is connected to the first heat exchange circulation pipe, and an exhaust valve is provided on the exhaust pipe.

[0016] The first heat exchange circulation pipe includes a first circulation branch pipe and a second circulation branch pipe. The liquid inlet branch pipe and the liquid outlet branch pipe are both connected to the first circulation branch pipe, and both ends of the second circulation branch pipe are connected to the first circulation branch pipe. A gas boiler, a circulation pump, and at least two heating control valves are provided on the second circulation branch pipe. The gas boiler is used to heat the heat exchange medium. The circulation pump is located on one side of the gas boiler, and the heating control valves are located on both sides of the gas boiler.

[0017] Furthermore, the reaction unit has a feed port at the top for inputting liquid and a discharge port at the bottom for outputting liquid. The area also includes a feeding zone and a discharging zone, with a feed pipe connected to the feeding zone and a discharge pipe connected to the discharging zone. As the rotary distribution valve rotates, each reaction unit can sequentially connect to the feeding zone and the discharging zone. When connecting to the feeding zone, the feed pipe connects to the feed port on the corresponding reaction unit; when connecting to the discharging zone, the discharge pipe connects to the discharge port on the corresponding reaction unit. A first heat exchanger is provided between the feed pipe and the discharging pipe for heat exchange between the liquid in the feed pipe and the liquid in the discharging pipe.

[0018] Furthermore, a second heat exchanger is provided between the feeding pipe and the second heat exchange circulation pipe, and the second heat exchanger is used to exchange heat between the liquid in the feeding pipe and the heat exchange medium in the second heat exchange circulation pipe.

[0019] Furthermore, it also includes a cooling water pipe, and a third heat exchanger is provided between the cooling water pipe and the second heat exchange circulation pipe. The third heat exchanger is used to exchange heat between the cooling water in the cooling water pipe and the heat exchange medium in the second heat exchange circulation pipe.

[0020] Furthermore, a short pipe is connected between the heat exchange inlet and the heat exchange outlet of each reaction unit, and a short-connection valve is provided on the short pipe.

[0021] A method for preparing lithium iron phosphate, using the aforementioned continuously heat-exchangeable fluid contact reaction equipment.

[0022] The present invention has the following beneficial effects:

[0023] 1. This invention provides a fluid contact reaction device with continuous heat exchange. In use, each reaction unit can provide a place for the liquid to contact and react, and is sequentially connected to the heating zone and cooling zone on the rotary distribution valve. When connecting the heating zone and cooling zone, the heat exchange medium can be introduced into the corresponding reaction unit through the rotary distribution valve to exchange heat with the liquid. As the rotary distribution valve rotates and switches, the liquid can be continuously heat exchanged, which can accelerate the heating and cooling speed of the liquid inside the reaction unit.

[0024] 2. This invention provides a fluid contact reaction device with continuous heat exchange. A first heat exchange circulation pipe and a second heat exchange circulation pipe are connected between the heating zone and the cooling zone. In use, the high-temperature heat exchange medium after heat exchange in the cooling zone can be drawn out and guided to the reaction unit corresponding to the heating zone for heat exchange, assisting in the heating of the liquid in the corresponding reaction unit. Similarly, the low-temperature heat exchange medium after heat exchange in the heating zone can be drawn out and guided to the reaction unit corresponding to the cooling zone for heat exchange, assisting in the cooling of the liquid in the corresponding reaction unit, effectively improving the thermal energy utilization rate.

[0025] 3. This invention provides a fluid contact reaction device with continuous heat exchange. The device connects heating, isothermal, and cooling preparation steps in series, and can perform gradient heating and cooling of the liquid material. It is especially suitable for the preparation of lithium iron phosphate by a fully wet process.

[0026] 4. This invention provides a method for preparing lithium iron phosphate, in which the liquid temperature rises and falls rapidly and the thermal energy utilization rate is high.

[0027] 5. This invention can broaden the application scenarios of rotary distribution valves. Attached Figure Description

[0028] Figure 1This is a process flow diagram of the present invention.

[0029] Figure 2 This is a schematic diagram of the heat exchange cycle process of the present invention.

[0030] Figure 3 This is a schematic diagram of the reaction unit structure of the present invention.

[0031] Figure 4 This is a simplified process flow diagram (I) of the present invention.

[0032] Figure 5 This is a simplified diagram (II) of the heat exchange process of the present invention.

[0033] Explanation of main component symbols: 1. Heat exchange structure; 2. Heat exchange inlet; 3. Heat exchange outlet; 4. Feed port; 5. Discharge port; 6. Feed pipe; 7. Discharge pipe; 8. Short-connector pipe; 9. Short-connector valve; 10. First heat exchange circulation pipe; 11. First circulation branch pipe; 12. Second circulation branch pipe; 13. Liquid inlet branch pipe; 14. Liquid inlet pump; 15. Liquid outlet branch pipe; 16. Expansion tank; 17. Oil filling port; 18. Exhaust port; 19. Oil replenishment port; 20. Oil replenishment pipe; 21. Oil replenishment valve; 22. Exhaust pipe; 23. Exhaust valve; 24. Gas boiler; 25. Circulation pump; 26. Second heat exchange circulation pipe; 27. First heat exchanger; 28. Second heat exchanger; 29. ​​Third heat exchanger; 30. Cooling water pipe. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] like Figure 1-3 As shown, the present invention discloses a fluid contact reaction device with continuous heat exchange, including a rotary distribution valve and multiple reaction units.

[0037] The rotary distribution valve has N pairs of rotatable and switchable fluid channels divided into M regions. The N pairs of fluid channels are distributed in the M regions, where N ≥ M ≥ 2. Each of the M regions includes at least one heating zone and one cooling zone. Both the heating and cooling zones have heat exchange medium inlets and outlets. Each pair of fluid channels includes a feed fluid channel and a discharge fluid channel. The heat exchange medium inlet is the port of the feed fluid channel located on the fixed valve disc, and the heat exchange medium outlet is the port of the discharge fluid channel located on the fixed valve disc.

[0038] The reaction unit adopts a jacketed reactor. The top of the reaction unit has a feed port 4 for inputting the liquid, and the bottom has a discharge port 5 for outputting the liquid. Each reaction unit is equipped with a heat exchange structure 1, i.e., a jacket structure, for heat exchange. Each heat exchange structure 1 of the reaction unit has a heat exchange inlet and a heat exchange outlet 3 for the heat exchange medium to enter and exit. The reaction unit is configured one-to-one with the N pairs of fluid channels on the rotary distribution valve. As the rotary distribution valve rotates, each reaction unit can be connected to the heating zone and the cooling zone respectively. During connection, the heat exchange medium inlet is connected to the heat exchange inlet on the corresponding reaction unit, and the heat exchange medium outlet is connected to the heat exchange outlet 3 on the corresponding reaction unit.

[0039] During the heating zone, the reaction unit heats the feed liquid. At this time, a high-temperature heat exchange medium is introduced into the reaction unit through the heat exchange medium inlet in the heating zone to assist in the rapid heating of the feed liquid. During the cooling zone, the reaction unit cools the feed liquid. At this time, a low-temperature heat exchange medium is introduced into the reaction unit through the heat exchange medium inlet in the cooling zone to assist in the rapid cooling of the feed liquid. After heat exchange is completed, the heat exchange medium can be discharged through heat exchange outlet 3 and the corresponding heat exchange medium outlet.

[0040] In addition to the heating and cooling zones mentioned above, taking the preparation of lithium iron phosphate as an example, the M zones also include a temperature regulating zone and a constant temperature zone. These zones are arranged sequentially along the rotation direction of the rotary distribution valve. The temperature regulating and constant temperature zones also have the aforementioned heat exchange medium inlet and outlet. As the rotary distribution valve rotates, each reaction unit can sequentially connect to the heating, temperature regulating, constant temperature, and cooling zones. Similarly, during connection, the heat exchange medium inlet connects to the heat exchange inlet of the corresponding reaction unit, and the heat exchange medium outlet connects to the heat exchange outlet 3 of the corresponding reaction unit.

[0041] During docking in the temperature-regulating zone, the reaction unit heats the feed liquid. High-temperature heat exchange medium can be introduced into the reaction unit through the heat exchange medium inlet in the temperature-regulating zone to assist in raising the temperature of the feed liquid. During docking in the constant-temperature zone, heat exchange medium can be introduced through the heat exchange medium inlet in the constant-temperature zone to assist the reaction unit in maintaining the temperature of the feed liquid at approximately the set value.

[0042] Typically, the M zones include a feeding zone and a discharging zone. These zones—feeding zone, heating zone, temperature control zone, constant temperature zone, cooling zone, and discharging zone—are arranged in a cycle along the rotation direction of the rotary distribution valve. The feeding zone is connected to a feeding pipe 6 via a fluid channel, and the discharging zone is connected to a discharging pipe 7 via a fluid channel. When connecting to the feeding zone, the feeding port 4 on the reaction unit connects to the feeding pipe 6 for feeding. When connecting to the discharging zone, the discharging port 5 on the reaction unit connects to the discharging pipe 7 for discharging.

[0043] In this embodiment, a total of twenty reaction units are provided. Among them, the heating zone and the cooling zone each connect to seven reaction units, the constant temperature zone connects to three reaction units, and the temperature adjustment zone, the feeding zone, and the unloading zone each connect to one reaction unit. The seven reaction units connected to the heating zone, the seven reaction units connected to the cooling zone, and the three reaction units connected to the constant temperature zone are connected in series and / or in parallel through fluid channels in the corresponding areas to perform heat exchange synchronously.

[0044] As the rotary distribution valve rotates, each reaction unit can sequentially connect to the feeding zone, heating zone, temperature control zone, constant temperature zone, cooling zone, and discharging zone. Each rotation of the rotary distribution valve moves each reaction unit one position along the circulation direction, connecting it to the next pair of fluid channels, for example, from... Figure 4 transitioning to the middle state Figure 5 In the intermediate state, reaction unit 1# changes from the state of the last pair of fluid channels in the original docking cooling zone to the state of the fluid channels in the docking feeding zone, and reaction unit 2# changes from the state of the sixth pair of fluid channels in the original docking cooling zone to the state of the last pair of fluid channels in the docking cooling zone. The remaining reaction units follow the same pattern.

[0045] As can be seen, in the preparation of lithium iron phosphate, each reaction unit can be sequentially "moved" to the feeding zone, heating zone, temperature adjustment zone, constant temperature zone, cooling zone, and unloading zone as the rotary distribution valve rotates, with gradient heating and cooling, thus completing one lithium iron phosphate production task. During the preparation process, a heat-conducting medium can be introduced for heat exchange, and the heating and cooling rates of the liquid are relatively fast.

[0046] Based on this, a first heat exchange circulation pipe 10 is connected between the heat exchange medium inlet of the heating zone and the heat exchange medium outlet of the cooling zone, and a second heat exchange circulation pipe 26 is connected between the heat exchange medium outlet of the heating zone and the heat exchange medium inlet of the cooling zone. Through the first heat exchange circulation pipe 10, the high-temperature heat exchange medium after heat exchange in the cooling zone can be drawn out and guided to the reaction unit corresponding to the heating zone for heat exchange, assisting in the heating of the liquid in the corresponding reaction unit. Similarly, through the second heat exchange circulation pipe 26, the low-temperature heat exchange medium after heat exchange in the heating zone can be drawn out and guided to the reaction unit corresponding to the cooling zone for heat exchange, assisting in the cooling of the liquid in the corresponding reaction unit, effectively improving the thermal energy utilization rate.

[0047] Furthermore, the first heat exchange circulation pipe 10 is connected to several inlet branch pipes 13 and several outlet branch pipes 15. While the inlet branch pipes 13 connect to the heat exchange medium inlets in the heating zone, temperature adjustment zone and constant temperature zone respectively, the outlet branch pipes 15 connect to the heat exchange medium outlets in the temperature adjustment zone, constant temperature zone and cooling zone respectively. The heat exchange medium can be recycled and introduced into different zones for heat exchange, resulting in higher thermal energy utilization.

[0048] Preferably, the inlet branch pipes 13 correspond one-to-one with the heating zone, temperature adjustment zone, and constant temperature zone, and each inlet branch pipe 13 is equipped with an inlet pump 14. The flow rate of heat transfer oil entering the heating zone, temperature adjustment zone, and constant temperature zone can be controlled by frequency conversion adjustment of each inlet pump 14, thereby controlling the heat exchange of the reaction units in the heating group, temperature adjustment group, and constant temperature group, resulting in more precise temperature control.

[0049] In this embodiment, the heat exchange medium is heat transfer oil. That is, the heat exchange medium flowing through the heating zone, temperature regulating zone, and constant temperature zone to the corresponding reaction unit is hot oil, and the heat exchange medium flowing through the cooling zone to the corresponding reaction unit is cold oil. Correspondingly, the equipment also includes an expansion tank 16, an oil replenishment pipe 20, and an exhaust pipe 22. The expansion tank 16 has an oil filling port 17 and an exhaust port 18 at the top and an oil replenishment port 19 at the bottom. One end of the oil replenishment pipe 20 is connected to the oil replenishment port 19, and the other end is connected to the first heat exchange circulation pipe 10. An oil replenishment valve 21 is provided on the oil replenishment pipe 20. One end of the exhaust pipe 22 is connected to the exhaust port 18, and the other end is connected to the first heat exchange circulation pipe 10. An exhaust valve 23 is provided on the exhaust pipe 22. The first heat exchange circulation pipe 10 includes a first circulation branch pipe 11 and a second circulation branch pipe 12. The liquid inlet branch pipe 13 and the liquid outlet branch pipe 15 are both connected to the first circulation branch pipe 11, and both ends of the second circulation branch pipe 12 are connected to the first circulation branch pipe 11. The second circulation branch pipe 12 is equipped with a gas-fired boiler 24, a circulation pump 25, and at least two heating control valves. The gas-fired boiler 24 is used to heat the heat exchange medium, the circulation pump 25 is located on one side of the gas-fired boiler 24, and the heating control valves are located on both sides of the gas-fired boiler 24. The gas-fired boiler 24 heats the heat transfer oil during circulation, preventing insufficient oil temperature from affecting the heat exchange effect. The expansion tank 16 effectively extends the life of the heat transfer oil, indirectly protecting components such as the gas-fired boiler 24 and the circulation pump 25.

[0050] To further improve thermal energy utilization, the equipment is also equipped with a cooling water pipe 30, a first heat exchanger 27 between the feed pipe 6 and the discharge pipe 7, a second heat exchanger 28 between the feed pipe 6 and the second heat exchange circulation pipe 26, and a third heat exchanger 29 between the cooling water pipe 30 and the second heat exchange circulation pipe 26. The first heat exchanger 27 exchanges heat between the liquid in the feed pipe 6 and the liquid in the discharge pipe 7; the second heat exchanger 28 exchanges heat between the liquid in the feed pipe 6 and the heat exchange medium in the second heat exchange circulation pipe 26; and the third heat exchanger 29 exchanges heat between the cooling water in the cooling water pipe 30 and the heat exchange medium in the second heat exchange circulation pipe 26. These heat exchangers 27, 28, and 29 can compensate for any potential deficiency in the heat exchange area of ​​the reaction unit, further improving thermal energy utilization.

[0051] In addition, a short pipe 8 is connected between the heat exchange inlet 2 and the heat exchange outlet 3 on each reaction unit, and a short-connection valve 9 is installed on the short pipe 8. When the reaction temperature reaches the set value or when the reaction unit needs to be repaired, the short pipe 8 can be opened to stop the heat exchange with the liquid in the reaction unit.

[0052] As can be seen, the device uses a rotary distribution valve to distribute the heat exchange medium and combines it with the reaction unit to perform heating and cooling operations on the liquid. It can connect multiple steps such as heating, cooling and constant temperature to perform gradient heating and cooling and continuous heat exchange on the liquid. The heating and cooling speed is fast and the thermal energy utilization rate is high.

[0053] Example 2

[0054] Based on the above-described embodiment one, this invention also discloses a method for preparing lithium iron phosphate, which utilizes the aforementioned continuously heat-exchangeable fluid contact reaction equipment. This preparation method can be combined with a fully wet process, subjecting the feed liquid to gradient heating and cooling and continuous heat exchange to obtain lithium iron phosphate. The preparation process features rapid heating and cooling of the feed liquid and high thermal energy utilization.

[0055] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail to the invention without departing from the spirit and scope of the invention as defined in the appended claims are within the scope of protection of the invention.

Claims

1. A fluid contact reaction device with continuous heat exchange capability, characterized in that: Includes a rotary distribution valve and multiple reaction units; The rotary distribution valve is provided with M regions, M≥2, and the regions include at least a heating region and a cooling region. Each heating region and cooling region is provided with a heat exchange medium inlet and a heat exchange medium outlet. Each of the reaction units is provided with a heat exchange structure, and the heat exchange structure is provided with a heat exchange inlet and a heat exchange outlet for the heat exchange medium to enter and exit; as the rotary distribution valve rotates and switches, each of the reaction units can be connected to the heating zone and the cooling zone respectively. When connected, the heat exchange medium inlet is connected to the heat exchange inlet on the corresponding reaction unit, and the heat exchange medium outlet is connected to the heat exchange outlet on the corresponding reaction unit. A first heat exchange circulation pipe is connected between the heat exchange medium inlet of the heating zone and the heat exchange medium outlet of the cooling zone, and a second heat exchange circulation pipe is connected between the heat exchange medium outlet of the heating zone and the heat exchange medium inlet of the cooling zone. The region also includes a temperature control zone and a constant temperature zone, each of which is provided with a heat exchange medium inlet and a heat exchange medium outlet; as the rotary distribution valve rotates and switches, each reaction unit can be sequentially connected to the heating zone, temperature control zone, constant temperature zone, and cooling zone; The reaction unit has a feed port at the top for inputting liquid and a discharge port at the bottom for outputting liquid. The area also includes a feeding zone and a discharging zone. The feeding zone is connected to a feeding pipe, and the discharging zone is connected to a discharging pipe. As the rotary distribution valve rotates, each reaction unit can be connected to the feeding zone and the discharging zone in sequence. When connected to the feeding zone, the feeding pipe is connected to the feed port on the corresponding reaction unit. When connected to the discharging zone, the discharging pipe is connected to the discharging port on the corresponding reaction unit. A first heat exchanger is provided between the feed pipe and the discharge pipe, and the first heat exchanger is used to exchange heat between the liquid in the feed pipe and the liquid in the discharge pipe. A second heat exchanger is provided between the feeding pipe and the second heat exchange circulation pipe. The second heat exchanger is used to exchange heat between the liquid in the feeding pipe and the heat exchange medium in the second heat exchange circulation pipe.

2. The fluid contact reaction device with continuous heat exchange as described in claim 1, characterized in that: The first heat exchange circulation pipe is connected to several inlet branch pipes and outlet branch pipes. The first heat exchange circulation pipe is connected to the heat exchange medium inlet in the heating zone, the temperature adjustment zone and the constant temperature zone through the inlet branch pipes, and is connected to the heat exchange medium outlet in the temperature adjustment zone, the constant temperature zone and the cooling zone through the outlet branch pipes.

3. The fluid contact reaction device with continuous heat exchange as described in claim 2, characterized in that: Each liquid inlet branch pipe corresponds to one of the heating zone, temperature adjustment zone, and constant temperature zone, and each liquid inlet branch pipe is equipped with a liquid inlet pump.

4. The fluid contact reaction device with continuous heat exchange as described in claim 2, characterized in that: It also includes an expansion tank, an oil replenishment pipe, and an exhaust pipe; the expansion tank is provided with an oil filling port and an exhaust port at the top and an oil replenishment port at the bottom; one end of the oil replenishment pipe is connected to the oil replenishment port and the other end is connected to the first heat exchange circulation pipe, and an oil replenishment valve is provided on the oil replenishment pipe; one end of the exhaust pipe is connected to the exhaust port and the other end is connected to the first heat exchange circulation pipe, and an exhaust valve is provided on the exhaust pipe. The first heat exchange circulation pipe includes a first circulation branch pipe and a second circulation branch pipe. The liquid inlet branch pipe and the liquid outlet branch pipe are both connected to the first circulation branch pipe, and both ends of the second circulation branch pipe are connected to the first circulation branch pipe. A gas boiler, a circulation pump, and at least two heating control valves are provided on the second circulation branch pipe. The gas boiler is used to heat the heat exchange medium. The circulation pump is located on one side of the gas boiler, and the heating control valves are located on both sides of the gas boiler.

5. The fluid contact reaction device with continuous heat exchange as described in claim 1, characterized in that: It also includes a cooling water pipe, and a third heat exchanger is provided between the cooling water pipe and the second heat exchange circulation pipe. The third heat exchanger is used to exchange heat between the cooling water in the cooling water pipe and the heat exchange medium in the second heat exchange circulation pipe.

6. The fluid contact reaction device with continuous heat exchange as described in claim 1, characterized in that: Each of the reaction units is connected to a short pipe between the heat exchange inlet and the heat exchange outlet, and the short pipe is equipped with a short-connection valve.

7. A method for preparing lithium iron phosphate, characterized in that: The preparation is carried out using a fluid contact reaction apparatus with continuous heat exchange as described in any one of claims 1-6.

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